In the past, a catheter type imaging diagnostic apparatus has been widely used for diagnosing arteriosclerosis, for diagnosis before surgery on an occasion of an intravascular treatment by a balloon catheter and a high functional catheter such as a stent and the like, or for confirming results after surgery.
One example of an imaging diagnostic apparatus is an intravascular ultrasound diagnostic apparatus (IVUS: Intra-Vascular Ultra-Sound). Generally, the intravascular ultrasound diagnostic apparatus is a diagnostic apparatus which obtains vascular cross-section images, after an ultrasound transducer built-in probe is radially scanned in a blood vessel and a reflected wave (ultrasound echo) reflected by an intravascular biological tissue is received by the same ultrasound transducer, based on the strength of the ultrasound echo produced by applying an amplification process, detection or the like.
In addition, recently, in order to obtain cross-section images of higher resolution, there has been promoted a development of an optical coherence imaging diagnostic apparatus (OCT: Optical Coherent Tomography) which performs an imaging diagnosis by utilizing light coherence.
An optical coherence imaging diagnostic apparatus is a diagnostic apparatus in which reflected light from a specific point in the depth direction of the biological tissue is extracted by superimposing reflected light from the surface and the inside of a biological tissue when entering a low coherence measuring light (signal light) into the intravascular biological tissue and reference light which is obtained by dispersing the measuring light differently from that and whose light path length is in conformity therewith, and after converting that into an electric signal, a vascular cross-section image is obtained by converting it into image information.
In addition, recently there has been promoted also a development of an optical coherence imaging diagnostic apparatus utilizing wavelength scanning (OFDI: Optical Frequency Domain Imaging) which is an improvement type of optical coherence imaging diagnostic apparatus. The optical coherence imaging diagnostic apparatus utilizing wavelength scanning (OFDI) is a diagnostic apparatus in which reflected light from respective points in the depth direction of the biological tissue is extracted based on the differences of the frequency components by continuously changing wavelengths of the measuring light which enters an intravascular biological tissue, and vascular cross-section images are obtained by using the reflected light. In the case of the optical coherence imaging diagnostic apparatus utilizing wavelength scanning (OFDI), there is an advantage compared with an optical coherence imaging diagnostic apparatus (OCT) in that the moving portion for continuously varying the light path length of the reference light can be eliminated.
It is generally known that an optical fiber is used, for example, in a so-called optical coherence imaging diagnostic apparatus of the OCT and OFDI type, to transmit the measuring light. The optical fiber is an electric transmission line so referred to in an ultrasound imaging diagnostic apparatus, and the fiber is inserted into a driving shaft which transmits rotary driving force, and a portion of the fiber is fixed to the driving shaft.
In this optical coherence imaging diagnostic apparatus, a portion corresponding to the ultrasound transducer so referred to in the ultrasound imaging diagnostic apparatus is an optical component of a spacer, a rod lens and a prism or the like which is formed at a distal portion of the optical fiber. The light emanating from the optical fiber is focused by the aforesaid optical component and further, is emitted to the living body in a state of being bent in a direction approximately perpendicular with respect to the driving shaft.
Japanese Unexamined Patent Publication No. 2001-272332 and Japanese Unexamined Patent Publication No. 2003-35660 disclose that such an optical coherence imaging diagnostic apparatus can be constructed such that optical coherence images are produced, as mentioned above, by making a returned light (reflected light) obtained by illuminating a signal light to a living body which is a measuring object and a reference light interfere each other.
To generally explain this light path system, as shown in FIG. 20, a measuring light La emitted from a light source is split into a sample light Lo and a reference light Lr by a splitting unit (beam splitter) BS for splitting this measuring light La. The split sample light Lo is illuminated onto a biological tissue which is a measuring object. The returning sample light (returned light) Lo which is reflected from the biological tissue once again enters the beam splitter BS.
On the other hand, the reference light Lr split by the beam splitter BS is reflected by a reference mirror RM and again enters the beam splitter BS along the same light path. Here, it is designed such that the light path length (referred to as Lo) from the beam splitter BS to the biological tissue (surface thereof) and the light path length (referred to as Lr) from the beam splitter BS to the mirror RM will be approximately equal.
The reference light Lr entering into the beam splitter BS and the returned sample light Lo interfere optically, and the optically interfering light is enters a photo detector (photo diode) PD. Owing to a fact that the optically interfering light entering the photo detector PD is detected and demodulated, images of the tissue cross-section of the biological tissue can be obtained.
Japanese Unexamined Patent Publication No. 2000-321472 and Japanese Unexamined Patent Publication H8-262287 disclose an optical fiber arranged in a hollow of a flexible tube.
Though not explained in detail in FIG. 8 of Japanese Unexamined Patent Publication No. 2001-272332 and in FIG. 4 of Japanese Unexamined Patent Publication No. 2003-35660, the light path systems are coupled by optical fibers in order to obtain the optical coherence images mentioned above in connection with the optical coherence imaging diagnostic apparatus. Any of the light source, the optical fiber which is the light path from the light source to the beam splitter BS, the optical fiber which is the light path from the beam splitter BS to the reference mirror, and the reference mirror is housed in the main body of the imaging diagnostic apparatus (steering control device).
On the other hand, the optical fiber which handles the signal light for observing the biological tissue should be inevitably introduced to the outside of the optical coherence imaging diagnostic apparatus (hereinafter, referred to as apparatus main body) for a portion thereof. Also, in order to radially scan the biological tissue as mentioned above, it is necessary to insert and attach the driving shaft reached until the distal portion of the catheter sheath which goes into the inside of the biological tissue in the catheter sheath together with the optical fiber.
In order to transmit driving force to the driving shaft, there is mounted on the outside of the apparatus main body a scanner including a motor drive unit (depending on circumstances, a scanner having pullback function). With respect to the installation of this scanner, the optical fiber cable derived to the outside of the steering control device is coupled to the input terminal side of this scanner (which means the steering control device side). Then, the output terminal side of this scanner is coupled to the catheter device.
As mentioned above, the scanner usually has a construction separate from the steering control device and also, the optical fiber cable arranged between the scanner and the steering control device has one end coupled to the input terminal side of the scanner and concurrently an optical connector is mounted on the other end. Because this optical connector is coupled to the optical connector provided on the steering control device side, it is constructed so that the light path of the sample light Lo will be formed.
Also for the optical coherence imaging diagnostic apparatus without a scanner, it is not preferable for a catheter device which is disposable or for which disinfection is necessary every time to be directly mounted on a large-sized steering control device. It is preferable to employ a construction which is freely attachable and detachable with respect to the optical fiber cable for signal light extending from the apparatus and for that purpose, it is necessary also for the optical fiber cable derived to the outside of the apparatus main body to use an optical fiber cable.
In the case of image diagnosis performed using an optical fiber as in a case of this optical coherence imaging diagnostic apparatus, it is necessary to couple the space between the apparatus main body and the catheter device or the space between the apparatus main body and the scanner by using an optical fiber cable.
Here, for the optical fiber built-in in the optical fiber cable, there is used, as mentioned later, an optical fiber main body (optical fiber core line) composed of a core, a clad and a protection tube or an optical fiber main body (optical fiber core line) for which a buffer layer (silicone resin or the like) further intervenes between the clad and the protection tube. Alternatively, there is used a tensile strength type optical fiber main body (tensile strength type optical fiber core line) in which one of those optical fiber main bodies is further covered by a tensile strength fiber as a tension member and a tube for protection.
The optical fiber main body itself has weak tensile strength and even in a case of the tensile strength type optical fiber main body, it is not possible to obtain sufficient tensile strength. Thus, they are weak with respect to bending, expansion and contraction of the fiber. In particular, when the optical fiber main body is subjected to an applied expansion and contraction force, there is a fear that the optical fiber main body (in particular, the core line (core)) will slightly be expanded and contracted. When such expansion and contraction occur, the light path length handled for the sample light changes. In a case in which little change occurs in this light path length, the aimed interference cannot be obtained. In a worst case scenario, it becomes quite difficult, perhaps impossible, to obtain optical coherence images from the light after the earliest optical coherence.
Specifically, when the difference between the light path length (Lo) from the beam splitter BS to the biological tissue (surface thereof) and the light path length (Lr) from the beam splitter BS to the mirror RM exceeds around 5 mm to 7 mm, it becomes quite difficult, if not impossible, to obtain optical coherence images.
Consequently, with respect to the optical fiber wired on the outside of the apparatus main body, considerably cautious handling of the fiber must occur. However, as a practical matter, it is almost nearly impossible to perform a coupling operation (attaching, detaching operation) and a storing operation with respect to the optical coherence imaging diagnostic apparatus and further, to execute an actual diagnosis procedure or the like without applying stress (inclusive of bending, expansion and contraction or the like, hereinafter referred to as external stress) to the optical fiber handling the sample light at all.
Without realizing it, some sort of external stress is applied inevitably, and associated with this expansion of the optical fiber occurs. When such an external stress is applied, optical coherence images are disturbed. Consequently, it is necessary to exercise ingenuity such that the external stress will not be applied to the optical fiber.
Japanese Unexamined Patent Publication No. 2000-321472 and Japanese Unexamined Patent Publication H8-262287 disclose a construction in which an optical fiber is installed in a hollow of a flexible tube. With respect to the optical fiber used in the optical coherence imaging diagnostic apparatus, depending on the construction of the apparatus, it is necessary to provide an optical connector unit, but Japanese Unexamined Patent Publication No. 2000-321472 and Japanese Unexamined Patent Publication H8-262287 do not disclose a preferable structure for providing an optical connector unit.